The research areas covered by the Alveolar Biology Program included: (1) definition of the structural and functional properties of the alveolar lining layer in the adult lung and also at birth; (2) investigation of the biosynthetic processes of the alveolar cell and subcellular components; (3) investigation of the interrelationship between alveolar epithelia cell metamorphosis,, alterations of the surfactant system and selected pulmonary pathological processes (for example, O2 toxicity and O2 tolerance); (4) identification of the surfactant system in fetal pulmonary fluid, its maturation during fetal development and its formation of the alveolar lining layer at birth; and (5) studies of fetal pulmonary fluid and solute dynamics vis-a-vis the flux between alveolar space and pulmonary capillary in the developing fetus. Specifically we will be looking into (1) the interaction among dipalmitoyllecithin (DPL) and proteins T which, we feel, are the basic components of the surfactant system; (2) the problem of laboratory-induced artifacts in handling pulmonary extracts which may lead to erroneous conclusion about the nature of the surfactant system; (3) the significance of zero surface tension at the alveolar lining/air interface; (4) the isolation and chemical characterization of type II cell inclusion bodies and their biosynthetic functions; (5) the isolation, growth and culture and metabolic activity of cultured type II cells; (6) fate and turnover of normal constituents of pulmonary fluid such as DPL and proteins T; (7) the relationship between fetal respiratory activity and metabolism of components of the surfactant system; and (8) the interrelationship between proliferation of inclusion bodies, mitochondrial changes, DPL production, and lipid-protein secretion during O2 poisoning and tolerance.